In prior art blooming processes, such as in filter tow processes preparatory to manufacturing tobacco smoke filter rods, the two is removed from a bale and is spread by means of a pneumatic banding jet, then bloomed through use of semi-tension techniques in which alternate sections of the tow band are tensioned and relaxed with grooved metal rolls in order to deregister the fiber crimp and separate the filaments. Although relatively effective, a disadvantage of this method is that the tow must actually be stretched and tensioned to separate the filaments. This is detrimental because stretching and tensioning the fiber by use solely of the aforementioned semi-tension techniques, which usually also include the use of pretension rolls, can remove a portion of the crimp and diminish the usefulness of the tow for making filter rods having a range of pressure drop and removal characteristics, i.e. the "capability range" of the tow is diminished. This effect occurs with all semi-tension processes and becomes more severe as the process speed is increased. Semi-tension processes also do not generally separate the filaments in the tow band to an optimum degree. Consequently "tow yield", which is related to the pressure drop per unit weight that can be obtained from the fiber, is lost with a resultant increase in final filter cost.
"Capability range" is defined as the range of pressure drop and weight characteristics which can be obtained from a given tow item, when it is manufactured into a tobacco smoke filter of fixed length and diameter. Additional capability range such as can be obtained with the process disclosed herein is particularly important for high-speed processing of filter tow since capability range for a given tow item generally decreases as processing speed is increased. Loss in capability range can make it difficult if not impossible to obtain desired rod weight and pressure drop characteristics.
After the two is bloomed on semi-tension processes, it is generally sprayed with plasticizer for the purpose of ultimately bonding the filaments to one another to produce a firm rigid structure that will not soften or collapse during smoking. The plasticizer spray is generally applied to only one side of the bloomed tow band and, if examined carefully, is found to deposit primarily on the surface of the tow band. Failure of the plasticizer particles to penetrate the band occurs primarily as the result of inadequate separation of the filaments at the point of plasticizer application by these processes. Application of plasticizer from only one side, of course, compounds the problems. The end result is loss of rod firmness and less-than-optimum collapse characteristics.
This type of process can also suffer from band width variation through the plasticizer application, which generally causes plasticizer application level to vary.
Another process known as the Eastman E-60 process (Eastman Kodak Company), as discloed, for instance, in U.S. Pat. No. 3,258,823, utilizes air rather than tension to bloom or separate the filaments in the tow band. Because the tow band experiences less tension with this type of process, less crimp is removed from the fiber and longer "effective" capability ranges can be obtained. One major disadvantage of this process is that the tow emerging from the jet after blooming has a cylindrical rope-like form that is unsuitable for the application of plasticizer. Plasticizer is therefore applied prior to the jet with a double-sided contacting "wick type" applicator which applies plasticizer to both sides of the unbloomed tow band. Penetration of the band is poor but double-sided application partially offsets this problem. One problem that arises with this process is that the plasticizer apparently interferes with the pneumatic blooming or separation of the filaments. As a result yield is lost, especially when low denier per filament, high total denier tow items are processed.
Other disadvantages arise from the small cylindrical entrance to the jet used for the Eastman E-60 process which can cause the machine to break down if filter tow with defects such as splices, end couplings or cut edges is processed.
Other disadvantages arise from the contact-type wick application which can cause filament breakage in the tow band. Band width fluctuation over the application wicks can also cause plasticizer level variation.